The invention relates to mixtures comprising aminophosphonium salts (mixtures of substances), and to the preparation and use thereof.
Aminophosphonium compounds are used, as is evident from WO 98/32532 and WO 98/22413, as catalysts in the preparation of fluorine-containing compounds by a halogen-fluorine exchange reaction (halex reaction). Although the tetrakis(diethylamino)phosphonium bromide used in WO 98/32532 and WO 98/22413 gives good results, it has a very high dermal toxicity. The very high dermal toxicity of  less than 50 mg/kg body weight stands in the way of industrial use, however.
The object is to provide novel mixtures which comprise high proportions of tetrakisaminophosphonium salts and which are suitable as catalysts or constituent of catalyst systems for phase-transfer reactions, in particular for halogen-fluorine exchange reactions, have a lower dermal toxicity and reach or even exceed the results which can be achieved on use of tetrakis(diethylamino)phosphonium bromide. It is additionally intended that preparation of these mixtures even in industrial quantities be possible in a comparatively simple manner at reasonable expense.
This object is surprisingly achieved by mixtures comprising from 70 to 99.5% by weight of a compound of the formula (R)4P+Xxe2x88x92 (1) and from 30 to 0.5% by weight of a compound of the formula (R)3Pxe2x95x90O (2), where R is in each case a radical 
and Xxe2x88x92 is an inorganic or organic anion or the equivalent of a multiply charged inorganic or organic anion.
The mixtures comprise high proportions of the compounds of the formula (R)4P+Xxe2x88x92 (1), namely the appropriate tetrakis(pyrrolidino)phosphonium salts or the tetrakis(piperidino)phosphonium salts. The compounds (R)3Pxe2x95x90O present in the mixture surprisingly have no adverse effects on the catalytic activity so that the mixtures can be employed directly as catalyst or catalyst component.
The dermal toxicity both for tetrakis(pyrrolidino)phosphonium chloride and for tetrakis(piperidino)phosphonium chloride is unexpectedly significantly less than that of tetrakis(diethylamino)phosphonium bromide, although there are no pronounced differences in relation to the molecular structure/molecular size and molecular mass of the tetrakisphosphonium cation. The dermal toxicity of tetrakis(piperidino)phosphonium chloride is xcx9c200 mg/kg body weight, that of tetrakis(pyrrolidino)phosphonium chloride is xcx9c390 mg/kg body weight, and is thus considerably less than that of tetrakis(diethylamino)phosphonium bromide. The data for the dermal toxicities of tetrakis(diethylamino)phosphonium bromide, tetrakis(piperidino)phosphonium chloride and tetrakis(pyrrolidino)phosphonium chloride are derived from our own measurements.
The present invention relates in particular to mixtures comprising 75 to 99, preferably 80 to 98, particularly preferably 85 to 95, % by weight of the compound (R)4P+Xxe2x88x92 (1) and 25 to 1, preferably 20 to 2, particularly preferably 15 to 5, % by weight of the compound (R)3Pxe2x95x90O (2). R isxe2x80x94as already stated previouslyxe2x80x94both in the compounds (1) and in the compounds (2) a pyrrolidino or piperidino radical, in particular a pyrrolidino radical.
Xxe2x88x92 in the compounds of the formula (1) is Fxe2x88x92, Cl31 , Brxe2x88x92, Ixe2x88x92, ClO4xe2x88x92, BF4xe2x80x94, PF6xe2x88x92, NO3xe2x88x92, HSO4xe2x88x92, xc2xd SO42xe2x88x92, H2PO4xe2x88x92, xc2xd HPO42xe2x88x92, ⅓ PO43xe2x88x92, Rxe2x80x3xe2x80x94COO, where Rxe2x80x3 is an alkyl radical having 1 to 9 carbon atoms, a phenyl radical, benzyl radical or naphthyl radical, Rxe2x80x2xe2x80x3xe2x80x94SO3xe2x88x92, where Rxe2x80x2xe2x80x3 is an alkyl radical having 1 to 18 carbon atoms, a phenyl radical, tolyl radical or naphthyl radical, HCO3xe2x88x92, xc2xd CO32xe2x88x92 or {fraction (1/2)} C6H4(COOxe2x88x92)2. Xxe2x88x92 is, in particular, Fxe2x88x92, Clxe2x88x92, Brxe2x88x92, Ixe2x88x92, BF4xe2x88x92, PF6xe2x88x92 or xc2xd SO42xe2x88x92, preferably Fxe2x88x92, Clxe2x88x92 or Brxe2x88x92, particularly preferably Clxe2x88x92.
The mixtures normally result as mixtures of substances consisting of 95 to 100, in particular 96 to 99.5, preferably 97 to 99, % by weight of the mixture comprising the compounds (R)4P+Xxe2x88x92 and (R)3Pxe2x95x90O and 5 to 0, in particular 5 to 0.5, preferably 3 to 1, % by weight of volatile constituents. Volatile constituents which may still be present are, for example, residues of unreacted starting materials and solvents. However, it is possible to remove the volatile constituents very substantially or completely.
G. N. Koidan et al., describe in J. Gen. Chem. USSR (Engl. Transl.) 52, 1982, pages 1779 to 1787, a multistage preparation of tetrakis(piperidino)phosphonium bromide. This entails initial reaction of a compound of the formula (R2N)3P+HalHalxe2x88x92 with ammonia, and preparation from the reaction product which is formed, with elimination of water, of a triamide of an iminophosphoric acid (phosphorimidic triamide). 
The triamide of the iminophosphoric acid is then converted with 1,5-dibromopentane in accordance with the following reaction equations
xe2x80x83(R2N)3Pxe2x95x90NH+Br(CH2)5Brxe2x86x92(R2N)3Pxe2x95x90Nxe2x80x94(CH2)5xe2x80x94Brxe2x80x83xe2x80x833.

by a ring-closure reaction into tetrakis(piperidino)phosphonium bromide.
This type of synthesis is very complicated, requires several reaction stages and leads to a reaction product which, besides the tetrakis(piperidino)phosphonium bromide, still contains strongly basic compounds of the formula (R2N)3Pxe2x95x90NH and (R2N)3Pxe2x95x90Nxe2x80x94(CH2)5Br. These compounds interfere with the catalytic activity, in particular with the selectivity for particular halex reactions.
There is consequently a need to provide a process for preparing tetrakis(piperidino)phosphonium salts which avoids the aforementioned disadvantages, can be implemented even industrially in a straightforward manner and makes the required products available in good yields.
The object is achieved by a process for preparing the aforementioned mixtures comprising the compounds (R)4P+Xxe2x88x92 and (R)3Pxe2x95x90O. It comprises reacting a phosphorus pentahalide with pyrrolidine or piperidine in the molar ratio 1:6 to 1:50 in the presence of an inert solvent, initially at 10 to 80xc2x0 C., subsequently continuing the reaction at 90 to 180xc2x0 C., treating the resulting reaction product at 0 to 80xc2x0 C. with aqueous alkali at a pH of 7 to 15, and separating aqueous and organic phase from one another.
Normally pyrrolidine or piperidine is added to the mixture of phosphorus pentahalide and solvent, but the reverse procedure is also possible. The reaction moreover proceeds initially in the aforementioned temperature range. The temperature should ordinarily be kept in the stated temperature range, where appropriate by cooling. Care must be taken that the reactants are thoroughly mixed. This reaction step is particularly straightforward when pyrrolidine or piperidine is added at a rate such that said temperature range is maintained.
Following this reaction step the reaction is, as stated above, continued at a higher temperature, at which the required tetrakis(pyrrolidino)- or tetrakis-(piperidino)phosphonium salt is formed.
Long reaction times and high reaction temperatures favor the formation of the tetrakis(pyrrolidino)- or tetrakis(piperidino)phosphonium salts, whereas shorter reaction times and low reaction temperatures lead to mixtures with an increased proportion of (R)3Pxe2x95x90O compounds.
After completion of this reaction, the reaction product is, as already mentioned above, treated at a temperature of from 0 to 80xc2x0 C. with an aqueous alkali. The amount of alkali employed is such that a pH of 7 to 15 is maintained during the treatment. The treatment with the aqueous alkali leads to hydrolysis of hydrolyzable constituents of the reaction product. The compounds of the formula (R)3Pxe2x95x90O (2) presumably result from this hydrolysis and may be produced in varying amounts. A further effect of the treatment with aqueous alkali is that the hydrohalides of pyrrolidine or piperidine which are formed during the reaction are neutralized, and pyrrolidine or piperidine is liberated. The liberated pyrrolidine or piperidine can be recovered and reused in the reaction.
The aqueous phase is separated from the organic phase which contains the required reaction product, solvent, and excess pyrrolidine or piperidine used and/or that liberated from the hydrohalides. The organic phase is then concentrated, for example by vacuum distillation, to dryness. The solid produced thereby contains the mixtures according to the invention and can be employed directly, for example as catalyst or catalyst constituent.
In the light of the prior art described in J. Gen. Chem. USSR (Engl. Transl.) 52, 1982, pages 1779 to 1787, it may be regarded as surprising that the tetrakis(piperidino)phosphonium salts can be prepared directly by reacting a phosphorus pentahalide with piperidine.
In view of the severe reaction conditions used in the preparation according to the invention, in particular the high temperatures, it is not to be expected that it is possible to prepare a mixture comprising essentially only two compounds with a high proportion of tetrakis(pyrrolidino)- or tetrakis(piperidino)phosphonium salts and employable directly as catalyst or catalyst constituent.
Reactions taking place at high temperatures normally lead to reaction products consisting of a large number of different reaction products and having impurities preventing use as catalystxe2x80x94without the need to undertake elaborate additional purification. Catalyst poisons act, as the skilled worker knows, even in very small quantities. The mixtures contain no interfering (R)3Pxe2x95x90NRxe2x80x2 (Rxe2x80x2=hydrogen, alkyl, alkenyl having 1 to 6 carbon atoms or xe2x80x94(CH2)xHal, where x=2 to 5 and Hal is Cl or Br). Compounds of this type are known to be strong bases (see, for example: R. Schwesinger et. al., Chem. Ber.1994, 127, 2435-2454, in particular page 2440 herein).
In a large number of cases, the phosphorus pentahalide is reacted with pyrrolidine or piperidine in the molar ratio 1:7 to 1:25, in particular 1:8 to 1:16, preferably 1:8 to 1:14. Phosphorus pentahalide is reacted with pyrrolidine or piperidine, as mentioned at the outset, initially at xe2x88x9220 to 80, in particular 20 to 75, preferably 40 to 70xc2x0 C.
The inert solvent employed is an aliphatic, cycloaliphatic or aromatic hydrocarbon or a mono- or polychlorinated aliphatic, cycloaliphatic or aromatic hydrocarbon.
Examples of very suitable inert solvents are hexane, cyclohexane, methylcyclohexane, toluene, ethylbenzene, mesitylene, o-xylene, m-xylene, p-xylene, technical mixtures of isomeric xylenes, methylene chloride, tetrachloroethane, chlorobenzene, dichlorobenzene or chlorotoluene, in particular o-xylene, m-xylene, p-xylene, technical mixtures of isomeric xylenes, chlorobenzene. Mixtures of solvents can also be used.
Use of excess pyrrolidine or piperidine as solvent is likewise suitable. In this case, phosphorus pentahalide suspended or dissolved in an inert solvent, but not in pyrrolidine or piperidine, is metered in to pyrrolidine or piperidine, with mixing.
The reaction is continued, as already mentioned above, at 90 to 180, preferably 100 to 170, preferably 120 to 150xc2x0 C.
It is particularly simple to continue the reaction under reflux conditions, choosing a solvent which has a boiling point within the aforementioned temperature ranges.
However, it is also possible to carry out the reaction under pressure. It is thus also possible, if required, to employ solvents with lower boiling points.
In a particular variant, phosphorus pentachloride or phosphorus pentabromide, in particular phosphorus pentachloride, is employed as phosphorus pentahalide. It is also possible to prepare the phosphorus pentahalide in a preceding reaction step from the corresponding phosphorus trihalide and the halogen.
After completion of the reaction, the reaction product is treated, as already mentioned, at 0 to 100, in particular 10 to 70, preferably 25 to 50xc2x0 C. with aqueous alkali at a pH of 7 to 15, in particular 8 to 14.5, preferably 9 to 14. An example of a suitable aqueous alkali is a 5 to 50, in particular 15 to 30, preferably 15 to 25, % by weight of aqueous alkali metal or alkaline earth metal hydroxide solution. It is particularly simple to use a corresponding aqueous NaOH or KOH, in particular an NaOH, solution. It has proven suitable in many cases to use a 20 to 25% strength aqueous NaOH or KOH, in particular NaOH.
Care must be taken that mixing is thorough during the treatment of the reaction product with the alkali.
Following the treatment of the reaction product with the alkali, the aqueous phase is separated from the organic phase. The mixtures comprising the compound (R)4P+Xxe2x88x92 and (R)3Pxe2x95x90O are present in the organic phase. Removal of volatile constituents, which include the solvent and pyrrolidine or piperidine still present, results in the mixtures as solid. If required, it is possible to increase the proportion of tetrakis(pyrrolidino)phosphonium salts or tetrakis(piperidino)phosphonium salts by recrystallization. The Xxe2x88x92=Clxe2x88x92 or Brxe2x88x92 can be exchanged for other of the above mentioned anions by salt metathesis, if desired.
The invention further relates to the use of the mixtures described above in detail which comprise the compound of the formula (R)4P+Xxe2x88x92 (1) and the compound of the formula (R)3Pxe2x95x90O (2), in which R and Xxe2x88x92 have the aforementioned meaning, as catalyst or cocatalyst for phase-transfer reactions, nucleophilic substitution reactions or halogen-fluorine exchange reactions, in particular for phase-transfer reactions or halogen-fluorine exchange reactions, preferably for halogen-fluorine exchange reactions.
Suitable as catalyst for halogen-fluorine exchange reactions (halex reactions) are, for example, mixtures of substances comprising one of the mixtures described above which comprise the compound of the formula (R)4P+Xxe2x88x92 (1) and the compound of the formula (R)3Pxe2x95x90O (2), in which R and Xxe2x88x92 have the aforementioned meaning, and at least one compound selected from the group of quaternary ammonium compounds of the formula 
quaternary ammonium salts or phosphonium salts of the formula 
polyethers of the formula R10xe2x80x94(Oxe2x80x94CxH2x)sxe2x80x94OR11 (5) and crown ethers, in which in formula (3), R1, R2 and R3 are identical or different and are a linear or branched radical of the formula xe2x80x94(CpH2pO)rR5 in which R5 is hydrogen or a linear or branched alkyl radical having 1 to 16 carbon atoms, p is an integer from 1 to 10 and r is an integer from 1 to 15;
or a linear or branched alkyl radical having 1 to 30 carbon atoms;
or an unsubstituted phenyl or naphthyl radical, or a substituted phenyl or naphthyl radical, where the substituents have the meaning of halogen, C1-C4-alkyl, C1-C4-alkoxy, nitro or cyano;
R4 is a linear or branched radical of the formula xe2x80x94(CpH2pO)rR5; and
Yxe2x88x92 is an inorganic anion;
and in formula (4)
R6, R7, R8 and R9 are identical or different and are a linear or branched alkyl radical having 1 to 22 carbon atoms; or an unsubstituted or substituted aryl radical or a C1-C4-alkylaryl radical, where aryl has the meaning of phenyl or naphthyl, and said substituents are halogen, C1-C4-alkyl, C1-C4-alkoxy, nitro or cyano; Z has the meaning of N or P, and Yxe2x88x92 is an inorganic anion;
and in formula (5)
R10 and R11 are identical or different and are a linear or branched alkyl radical having 1 to 16 carbon atoms;
x is an integer from 2 to 6 and
s is an integer from 1 to 60;
or one of the radicals R10 and R11 is hydrogen and the other of the radicals is a linear or branched alkyl radical having 1 to 16 carbon atoms,
x is an integer from 2 to 6 and s is an integer from 2 to 50, or the radicals R10 and R11 are hydrogen, x is an integer from 2 to 6 and s is an integer from 3 to 5.
Suitable catalysts for halogen-fluorine exchange reactions are mixtures of substances comprising one of the mixtures described above comprising the compound (R)4P+Xxe2x88x92 and the compound (R)3Pxe2x95x90O, and at least one compound selected from a group of quaternary ammonium compounds of the formula (3), quaternary ammonium salts and phosphonium salts of the formula (4), polyethers of the formula (5) and crown ethers, in which in formula (3), R1, R2 and R3 are identical or different and are a linear or branched radical of the formula xe2x80x94(CpH2pO)rR5 in which R5 is hydrogen or a linear or branched alkyl radical having 1 to 8 carbon atoms, p is an integer from 1 to 5 and r is an integer from 2 to 10; or a linear or branched alkyl radical having 1 to 18 carbon atoms; or an unsubstituted phenyl or naphthyl radical; R4 is a linear or branched radical of the formula xe2x80x94(CpH2pO)rR5, in which R5 is hydrogen or a linear or branched alkyl radical having 1 to 8 carbon atoms, p is an integer from 1 to 5 and r is an integer from 2 to 10. Particularly of interest as catalyst for halogen-fluorine exchange reactions are mixtures of substances which comprise one of the mixtures described above and at least one compound from the group of quaternary ammonium compounds of the formula (3).
The mixtures of substances normally comprise 5 to 95% by weight, in particular 20 to 80% by weight, preferably 25 to 75% by weight, of a mixture comprising the compound (R)4P+Xxe2x88x92 and (R)3Pxe2x95x90O. The residual 95 to 5% by weight, in particular 80 to 20% by weight, preferably 75 to 25% by weight, of the mixtures of substances are accounted for by the remainder, namely at least one compound selected from the group of quaternary ammonium compounds of the formula (3), of quaternary ammonium or phosphonium salts of the formula (4), polyethers of the formula (5) and crown ethers, in particular at least one compound from the group of quaternary ammonium compounds of the formula (3).